Drive assembly for use under wide operating temperature ranges

ABSTRACT

In a drive assembly especially adapted for operation over a wide range of operating temperatures, the drive shaft of a drive motor is supported in a bearing plate. The drive shaft drives a driven wheel, preferably by means of a pinion in meshed engagement with the driven wheel, and the driven wheel is also mounted in the bearing plate laterally offset from the drive shaft. Compensation for any variations in operating temperature is provided by forming the drive shaft, the driven wheel and the bearing plate of synthetic plastic material having the same temperature coefficient of expansion.

Unite States ate't 1 Schubert et al.

[ Apr. '30, 1974 DRIVE ASSEMBLY FOR USE UNDER WIDE OPERATXNG TEMPERATURE RANGES [75] Inventors: Karl-Friedrich Schubert,

Bietigheim; Rolf-Dieter Deiss, Sachsenheim, both of Germany [22] Filed: Nov. 21, 1972 [2]] Appl. No.: 308,431

[30] 1 Foreign Application Priority Data Nov. 26, l97l Germany.. 7144560 [52] US. Cl 74/421 A [51] Int. Cl. F1611 l/20 [58] Field of Search .f. 74/421 A [56] References Cited UNITED STATES PATENTS 3,651,707 3/1972 Rees 74/421 A Primary ExaminerLeonard H. Gerin Attorney, Agent, or FirmToren, McGeady and Stanger STRACT In a drive assembly especially adapted for operation over a wide range of operating temperatures, the drive shaft of a drive motor is supported in a bearing plate. The drive shaft drives a driven wheel, preferably by means of a pinion in meshed engagement with the driven wheel, and the driven wheel is also mounted in the bearing plate laterally offset from the drive shaft. Compensation for any variations in operating temperature is provided by forming the drive shaft, the driven wheel and the bearing plate of synthetic plastic material having the same temperature coefficient of expansion.

7 Claims, 1 Drawing Figure DRIVE ASSEMBLY FOR USE UNDER WIDE OPERATING TEMPERATURE RANGES SUMMARY OF THE, INVENTION The present invention is directed to a drive assembly such as the drive for a flashing warning light, and, more particularly, it is directed to an arrangement of the drive assembly which operates effectively over a wide range of operating temperatures.

When using a drive assembly including an electric motor and a transmission gear for a flashing warning light, or for the windshield wiping system of a motor vehicle, a large operating temperature range from -40 to 60 C can be expected. It is necessary for the drive assembly to operate reliably and effectively over this large temperature range.

Though the electrical elements of the drive assembly present no great difficulties, major problems are experienced on the mechanical side, especially in maintaining the coupling between the drive motor and the transmission gear, in particular, when the parts involved are made from synthetic plastic materialfor the purpose of reducing costs. Because such materials expand greatly at high temperatures and contract correspondingly at low temperatures, effective transmission of the drivingpower is seriously impaired when gear wheels are used,

invention to provide a drive assembly including a drive motor and an associated gear wheel transmission mechanism which operates effectively over a very wide temperature range and without experiencing the disadvantages mentioned above- Therefore, based on the present invention, the drive assembly includes a drive motor,,a drive shaft connected to the motor which meshes with a driven gear wheel either directly or by means of a driving gear wheel and the drive shaft of the motor and the shaft of the driven gear are mounted in a common bearing plate. Tocompensate for expansion or'contraction due to a wide range of operating temperatures, at least the bearing plate and the driven gear wheel or the bearing plate along with both the drive shaft and the driven gear wheel are formed of a synthetic plastic material having substantially the same temperature coefficient of expansion.

In this arrangement, the degree of meshing between the drive and driven members does not change, because, as the temperature fluctuates, the distance be tween the-drive shaft of the motor and the bearing shaft of the driven gear wheel changes to the same extent as the dimensions of the various parts involved.

Simplification of the drive assembly can be achieved in a self-aligning bearing positioned in a seat formed integrally with the bearing plate.

If a dc. commutator motor is used, its construction can be simplified by forming the brush holders for the carbon brushes integrally with the bearing plate. In such an arrangement the number of individual parts can be reduced.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWING I In the drawing:

The drawing is a cross-sectional view of a drive assembly embodying the present invention.

DETAILED DESCRIPTION OF THE INVENTION As shown in the drawing, a drive motor 10 has a drive shaft 30 extending outwardly from the motor and mounted in a bearing plate 12 by means of. a selfaligning bearing 13 positioned in a seat 31 formed integrally in the bearing plate. The bearing is secured axially relative to the motor 10 on the commutator end of the drive shaft 30 by means of a washer 19 and a spring clip. 18 engaged within a groove in the drive shaft. On the opposite side of the bearing plate from the motor, the bearing is secured by a washer 20 and a'collar 21 of the drive shaft 30. The end 17 of the drive shaft 30 projecting outwardly from and on the opposite side of the bearing plate from the drive motor, is formed as a toothed pinion. On the side of the bearing plate facing the motor, an extension 22 of the bearing plate adjacent the commutator 23 of the drive motor serves as a holder for the carbon brushes.

The drive assembly includes a gear wheel 16 in meshed engagement with the toothed pinion 17 of the driving shaft, and the gear wheel can be directly connected, for example, to a rotating flashing warning.

light. The axis of rotation of the driven gear wheel 16 is spaced laterally from the axis of the drive shaft and thegear wheel is also mounted in the bearing plate 12 by means of a hollow stub shaft 24. The hollow stub shaft 24 may be formed separately from the bearing plate 12 and it may also be formed integrally with the bearing plate.

The two bushings 25, 26 permit rotation of the driven gear wheel 16 on the stub shaft 24.

Threaded into one end of the hollow stub shaft 24 is a set screw 28 with a connecting cable 27 so that an electrical connection can be provided for a rotating flashing warning light positioned within the opening 29 in the shaft 24.

The combination of the bearing plate 12 and the driven gear wheel 16 and, if desired, the drive shaft or a separate driving gear wheel connected to the drive shaft, are formed of a synthetic plastic material having the same or substantially the same temperature coefficient of expansion, so that the meshed engagement between the driven gear wheel 16 and the toothed pinion 17 remain substantially independent of ambient temperature changes. This occurs'because the distance between the drive shaft 30 and the stub shaft 24 changes to the same extent and in the same direction as the dimensions of the interengaging gear wheels.

What is claimed is:

l. A drive assembly comprising a bearing plate, a drive motor, a drive shaft connected to and extending from said drive motor, said drive shaft mounted in said bearing plate, a driven wheel arranged to be driven by said drive shaft, said driven wheel mounted in said drive shaft so that its axis is offset from the axis of said drive shaft, at least said bearing plate and said driven wheel are formed of synthetic plastic material having substantially the same temperature coefficient of expansion.

2. A drive assembly, as set forth in claim 1, wherein said driven wheel is a gear wheel, a toothed pinion formed on said drive shaft and disposed in meshed engagement with said driven wheel, and said drive shaft and pinion are formed of a synthetic plastic material having the same temperature coefficient of expansion as said bearing plate and driven wheel.

3. A drive assembly, as set forth in claim 1, wherein a hollow stub shaft is mounted in said bearing plate, and said driven wheel is rotationally mounted on said 4 stub shaft.

4. A drive assembly, as set forth in claim 3, wherein said stub shaft is formed integrally with said bearing plate. v

5. A drive assembly, as set forthin claim 2, wherein said bearing plate has a seat formed integrally therein, a self-aligning bearing mounted in the seat in said bearing plate, and said drive shaft mounted in and extend ing through said self-aligning bearing.

6. A drive assembly, as set forth in claim 5, wherein said pinion on said drive shaft is on the end of said drive shaft on the opposite side of said bearing plate from said drive motor.

7. A drive assembly, as set forth in claim 3,'wherein a set screw is threaded into said hollow stub shaft, and

a connecting cable is fitted in said set screw for effect- 

1. A drive assembly comprising a bearing plate, a drive motor, a drive shaft connected to and extending from said drive motor, said drive shaft mounted in said bearing plate, a driven wheel arranged to be driven by said drive shaft, said driven wheel mounted in said drive shaft so that its axis is offset from the axis of said drive shaft, at least said bearing plate and said driven wheel are formed of synthetic plastic material having substantially the same temperature coefficient of expansion.
 2. A drive assembly, as set forth in claim 1, wherein said driven wheel is a gear wheel, a toothed pinion formed on said drive shaft and disposed in meshed engagement with said driven wheel, and said drive shaft and pinion are formed of a synthetic plastic material having the same temperature coefficient of expansion as said bearing plate and driven wheel.
 3. A drive assembly, as set forth in claim 1, wherein a hollow stub shaft is mounted in said bearing plate, and said driven wheel is rotationally mounted on said stub shaft.
 4. A drive assembly, as set forth in claim 3, wherein said stub shaft is formed integrally with said bearing plate.
 5. A drive assembly, as set forth in claim 2, wherein said bearing plate has a seat formed integrally therein, a self-aligning bearing mounted in the seat in said bearing plate, and said drive shaft mounted in and extending through said self-aligning bearing.
 6. A drive assembly, as set forth in claim 5, wherein said pinion on said drive shaft is on the end of said drive shaft on the opposite side of said bearing plate from said drive motor.
 7. A drive assembly, as set forth in claim 3, wherein a set screw is threaded into said hollow stub shaft, and a connecting cable is fitted in said set screw for effecting the transmission of current to a device operatively associated with said driven wheel and said hollow stub shaft. 